Finally beat it, clear time of 8 hours, 28 minutes on Hard with 97.2% complete. Was going to search for all the collectibles, but said fuck it. Finding the all "Pow" ones that unlock bonus shit is gay as hell since there's no map icons for them. Did find all the upgrades, canisters, and costumes though.
Definitely worth the 15 bucks. Hard can be pretty hard, some boss fights are a total bitch, and the start of the game is brutal until you get some health upgrades. The only real complaint I have is that once you beat it it locks you out and you can't go back and finish collecting stuff. They should have let you do a New Game+ or restored you to right before the last area.